/*
 * Copyright 2018 The Cartographer Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef CARTOGRAPHER_SENSOR_COLLATOR_INTERFACE_H_
#define CARTOGRAPHER_SENSOR_COLLATOR_INTERFACE_H_

#include <functional>
#include <memory>
#include <vector>

#include "absl/container/flat_hash_set.h"
#include "absl/types/optional.h"
#include "cartographer/sensor/data.h"

namespace cartographer {
	namespace sensor {

		class CollatorInterface {
		public:
			using Callback =
				std::function<void(const std::string&, std::unique_ptr<Data>)>;

			CollatorInterface() {}
			virtual ~CollatorInterface() {}
			CollatorInterface(const CollatorInterface&) = delete;
			CollatorInterface& operator=(const CollatorInterface&) = delete;

			// Adds a trajectory to produce sorted sensor output for. Calls 'callback'
			// for each collated sensor data.
			virtual void AddTrajectory(
				int trajectory_id,
				const absl::flat_hash_set<std::string>& expected_sensor_ids,
				const Callback& callback) = 0;

			// Marks 'trajectory_id' as finished.
			virtual void FinishTrajectory(int trajectory_id) = 0;

			// Adds 'data' for 'trajectory_id' to be collated. 'data' must contain valid
			// sensor data. Sensor packets with matching 'data.sensor_id_' must be added
			// in time order.
			virtual void AddSensorData(int trajectory_id, std::unique_ptr<Data> data) = 0;

			// Dispatches all queued sensor packets. May only be called once.
			// AddSensorData may not be called after Flush.
			virtual void Flush() = 0;

			// Must only be called if at least one unfinished trajectory exists. Returns
			// the ID of the trajectory that needs more data before CollatorInterface is
			// unblocked. Returns 'nullopt' for implementations that do not wait for a
			// particular trajectory.
			virtual absl::optional<int> GetBlockingTrajectoryId() const = 0;
		};

	}  // namespace sensor
}  // namespace cartographer

#endif  // CARTOGRAPHER_SENSOR_COLLATOR_INTERFACE_H_
